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16 to 8 ohm ?

Discussion in 'Amps and Cabs [BG]' started by karxix, Feb 13, 2004.


  1. karxix

    karxix

    May 26, 2003
    lebanon
    hey
    i have this 100 watt combo that's 4x12 but is quite old so i don't have any technical data about it
    it has 4 16ohm 25 watt speakers, i was wondering what would happen if i replace those speakers with 8ohm 50 watt speakers...
    what would happen? to the amp and to the sound ?

    or to put it in another way:
    with less ohm ratings, would the amp want to output more power? or would it output the same power it usually would but the speakers would work more than higher ohm rating speakers since they have less resistance to the power flow?
     
  2. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    what kind of amp is it? It might be bad for your amp. You ought to just stick with 8 ohm speakers, but get more efficient ones. That will make more use of the power you do have.
     
  3. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    Depending on how the original speakers are interconnected (if it's a solid state amp, I presume that they're wired in parallel presenting a 4 ohm load to the amp...if it's a tube amp, could go either way) and how you'd interconnect the new speakers.

    If it's a solid state amp and you wired the new speakers in parallel creating a 1 ohm load, the amp would sound like the old amp driving the new speakers for a short while until it blew up.

    If you wired the speakers into two series groups, then connected the groups in parallel to render a 4 ohm load to the amp (and that's the impedance presented by the original 4 speakers (not 16 ohms)) the amp would continue to work and it would depend on how the new speakers sounded.

    In other words...you could probably get it to work but until you try it out, you'll have no idea how it will sound.

    What kind of combo bass amp has 4-12s anyway? The only 100 watt 4x12 combo that comes to mind is the Fender Quad Reverb, but that's a guitar amp.
     
  4. karxix

    karxix

    May 26, 2003
    lebanon
    it's an old 1980 4x12 marshall combo amp (100 watts) that i got for really cheap but i liked its tone so i have no complaints about the purchase
    i was just wondering if i could squeeze more power out of it or anything like that ...

    here's a picture of the back panel (i removed the back cover so u c the speakers)

    from the looks they're in series but i don't really know much about that so tell me what you think please

    and do you have any suggestions for any speakers that might work as you suggested?
     
  5. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    If you change those speakers out, can I buy the old ones off of you>
     
  6. karxix

    karxix

    May 26, 2003
    lebanon
    i forgot to mention that one of the reasons i want to change the speakers i that i'm worried they might be "tired" , they're like 20 years old,
    they sound really good now, but i think newer speakers would sound better!
     
  7. karxix

    karxix

    May 26, 2003
    lebanon
    hmm, that would depend on the conditions...+ i live in Lebanon, it will cost quite a bit to mail them...
    anyway, what would you want with old speakers? :confused:
     
  8. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    wow. that would be costly. I was going to make an inexpensive cabinet for a 60 watt guitar head.
     
  9. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    Presumably, the cabinet was designed for the speakers so putting newer speakers in might sound worse.

    I'd say run the originals until they fail then get them reconed.

    I think that, in my book, you win the prize for having the coolest bass combo amp ever.

    How much does the whole amp weigh? Also, what are its dimensions?
     
  10. karxix

    karxix

    May 26, 2003
    lebanon
    yeah, that was something else i was thinking of (the cab made for speakers)

    can you explain further about the reconing part? i've heard of recoiling but reconing is new to me ... btw, the cones are a bit "mushy" as you can see, but i'm not sure how much that affects the sound

    the amp is around 30-35 KG (as a maximum, maybe an extra 5kgs)
    sorry, i don't know how much in pounds that is, i think maybe 60-70 pounds
     
  11. That is amp is just TOO COOL to mess with. If it ain't broke (you know the rest)
     
  12. karxix

    karxix

    May 26, 2003
    lebanon
    yeah, i guess u got a point
    i changed my mind about get new speakers at the moment but keep the replies coming for the future in case some speaker blows or whatnot

    still waiting for a reply from Billy reagarding reconing
    and if you can please check if you can find any info about the amp in your Marshall book
    thanks!
    am going to bed now, it's 2:30 am , hehe!
     
  13. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Reconing usually involves replacing everything on the speaker except the basket and magnet. So you get new cone, surrounds, voice coil, ductcap, everything. If your reconer knows what he's doing and uses the correct parts, you'll end with with as-new speakers for less money than buying new ones.
     
  14. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    Not much info about the 2077 in "The History of Marshall" except a line in the Appendix.

    2077, 100 watts RMS, Bass Combo, 4x12, Made '73 - '78, 2 channels, send and return, solid state.

    I had an interesting thought on the way home from work tonight. Perhaps the only bass combo that could be cooler than yours would have been a Marshall Major combo (200 watt all tube, 4xKT88) with 4x15s... Such an amp would probably weigh 100 Kg (220 lbs).

    If you can find a "T" number stamped on one of the speaker's frames, I can look that up and provide general characteristics.
     
  15. karxix

    karxix

    May 26, 2003
    lebanon
    aha, ok, thanks alot!

    4x15 = *drools*

    i will check for that "T" number within the next 2 days, i kept the amp at our practice place (15 mins from here) , I will go there as soon as I can....will keep you updated!
     
  16. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    I was looking through my treasures (aka old Marshall catalogs and literature) and found an owner's manual for the 2099 bass head (it's a combined brochure for the 2098 lead and 2099 bass amps). The input jack scheme is a bit different than on your 2077 with just three input jacks...one for each channel and one for both channels at once. However, the control compliment is the same (I'm guessing)...Vol. 2, Vol. 1, Treble, Middle, Bass, Presence and Master Volume (from right to left).

    I'll try to scan the back page with suggested settings and post it.

    I imagine that the circuits are pretty similar because I got this manual at the dawn of my Marshall awareness back in 1974 or so.

    I still remember the day in 1974 when I visited the "big" music store in my area, in a town about 30 Km from home, and came face to face with a full Marshall stack... That store also carried Acoustic (and Fender and Peavey)...and Rickenbacker basses too!! Ahh, those were good times...
     
  17. Ahh... 25w Blackbacks...

    Really, brother, get some different speakers and sell them to a guitarist who will be more than happy to take them off your hands. I don't think those speakers are "tired" it's just that they're really not supposed to handle the kind of bottom end we expect out of a bass rig today. My Marshall 4x12 is technically a "bass" bottom, I really don't know how they determined what made a "bass" bottom, same speakers that were in any other 4x12. Anyway, that's my guitar cab, and I have newer bass cabs for my bass rig.
     
  18. karxix

    karxix

    May 26, 2003
    lebanon
    thanks alot billyB, looking forward to that thing, i'd like to know what the heck there are 3 volume knobs on the amp!heh

    golden boy...at the moment they're doing fine at practice and etc, i don't really need more bass than that, i only use the amp at practice so i'm fine with that
     
  19. Hey karxix,

    Keep in mind those speakers, especially not being reconed, are worth a bunch of money to guitarists. While every guitarist wants to have "pre-Rola Celestion Greenbacks" or just "Greenbacks," the Cream and Black covered speakers aren't that far behind. In terms of guitar tone, the Blackbacks are generally a bit brighter (which just may be a result of age on the speaker). If it were me, if I were going to use the amp in a practice/gig situation, I'd probably replace the speakers with something newer and either put the Blackbacks away someplace away from moisture and extreme dryness (not an attic, not the damp corner of the basement).

    One thing you really should keep in mind is that even though it's YOUR gear, anything you do to it affects the people that own it after you. Vintage gear is history, and it's a cool way to be involved in history.

    Rock well, brother!
     
  20. karxix

    karxix

    May 26, 2003
    lebanon
    ok, thanks for the info !
    + i liked the part about history, makes lots of sense!
    u seem to know about the speakers quite a bit, do you have any suggestion for replacements or anything that would fit fine with that cab or anything like that?